1) Field of the Invention
The present invention relates to a fuel cell system comprising a fuel cell made to generate electric energy through chemical reactions between hydrogen and oxygen, and effectively applicable to movable bodies such as vehicles, ships and portable generators.
2) Description of the Related Art
So far, there has been known a fuel cell system equipped with a fuel cell which generates electricity through the use of electrochemical reactions between hydrogen and oxygen (air). For example, a polyelectrolyte type fuel cell, considered as a drive source for vehicles and others, requires keeping a high polymer electrolyte membrane in a damp or wet condition.
In a case in which a vehicle equipped with such a fuel cell is deactivated or stopped under low-temperature environments, there is a possibility of freezing of moisture existing within the fuel cell or a reaction gas path (passage). In addition, in the case of a fuel cell system in which an unreacted gas (off-gas) emitted from a fuel cell is recirculated to the fuel cell through the use of a pump, there is a possibility of freezing of moisture left in the pump or valves.
In a case in which a fuel cell is activated under such low-temperature environments, there arises a problem in that difficulty is encountered in activating the fuel cell due to the hindrance of advance/arrival of reaction gases (hydrogen and air) to or at an electrolyte membrane stemming from freezing, the clogging of a reaction gas path, a pump locked state, or others.